Experimental data & uncertainty · SL/HL
Calibration Curve & Unknown Concentration Calculator
Paste standard concentrations and responses. The fit is ordinary least squares with concentration treated as x.
Your values
Start with the example or enter your own values. Use a dot for decimals and e for scientific notation.
Calculated locally. No account or input upload.
Result & working
ExampleThe calculator is loading. The worked example is also shown below.
Step-by-step working
The formula
best-fit line: y = mx + c
unknown x = (y_unknown − c)/m
R² evaluates goodness of fit to the chosen linear trend
| Symbol | Meaning |
|---|---|
| x | Known standard concentration. |
| y | Instrument response such as absorbance when a linear calibration is justified. |
When to use this calculator
Check whether the unknown response lies within the calibrated range. Extrapolation beyond standards is less defensible and should be identified. A high R² alone does not prove the model or eliminate systematic error.
Worked example
The page opens with these example values. The result below is pre-generated for reference.
- OLS fit: y = 0.8514286x + 0.01428571
- R² = 0.9997073
- x_unknown = (y_unknown − c)/m = (0.44 − (0.01428571)) / 0.8514286 = 0.5 mol dm⁻³
0.5 mol dm⁻³
Common mistakes
- A calibration curve should use standards prepared and measured under conditions appropriate to the method.